Apparatus and method of flame or combustion rate



March 3, 1964 w. L. LIVINGSTON 3,123,027

APPARATUS AND METHOD OF FLAME 0R COMBUSTION RATE DETECTION IN ACOMBUSTION CHAMBER Original Filed Nov. 3, 1958 s Sheets-Sheet 1 l2 A|R\FUEL [0 kg 20 J 26 28 I ATMOSPHERIGfi 0 PRESSURE g -025 L 3: a -+0.25 305 All Q I H005 -o.7s--o.5 o uni- 5 ,r l

Ii FIG 8 El; 'IE El? LL] 0 IL} INVENTOR. 2 WILLIAM L. LIVINGSTON AGENTMarch 1954 w. L. LIVINGSTON 3,123,027

APPARATUS AND METHOD OF FLAME OR COMBUSTION RATE DETECTION IN ACOMBUSTION CHAMBER Original Filed Nov. 3, 1958 3 Sheets-Sheet 2 I25INVENTOR I25 WILLIAM L. LIVINGSTON /24 AGENT I11 III FIG. 9

March 3, 1964 w. L. LIVINGSTON 3,123,027

APPARATUS AND METHOD OF FLAME OR COMBUSTION RATE 7 DETECTION IN ACOMBUSTION CHAMBER Original Filed Nov. 3, 1958 5 Sheets-Sheet 3 FRICTIONLOSS FIG. 7

In 2 6 05 sans's 8d cums T IN VEN TOR.

WILLIAM L. LIVINGSTON AGENT United States Patent 3,123,927 APPARATUS ANDMETHGD 0F FLANiE 0R COM- BUSTEQN RATE DETECTION IN A COMBUSTION CHAR/BERWilliam L. Livingston, Bloomfield, Conn, assignor to CombustionEngineering, inc, New York, N.Y., a corporation of Delaware Continuationof appiication Ser. No. 771,375, Nov. 3, 3358. This application .lune19, 1962, Ser. No. 205,483 Claims. (Cl. 11023) The present applicationis a continuation of an original application Serial No. 771,375 filed inthe name of William L. Livingston on November 3, 1958, now abandoned.

The invention relates to combustion sensing and indicating apparatus andmethod as employed in connection with a combustion chamber, and is moreparticularly concerned with an indicating method and system for sensingdifference in combustion rate such as detecting the absence or presenceof combustion or flame in the chamber and transmitting this informationto a signal or other indicating device located at a control point remotefrom the combustion chamber.

My invention can readily be employed in connection with a wide varietyof combustion chambers or furnaces. it especially finds important anduseful application as indicating means for reporting differences incombustion rate or for detecting the presence of flame in furnaces ofsteam generators, and in igniter apparatus employed in connectiontherewith.

Such igniter apparatus usually takes the form of an auxiliary burneralso called pilot or igniter torch, using oil or gas to ignite otherfuel streams such as pulverized cofi delivered into a furnace as bymeans of tilting burners or the like. One such igniter torch and themanner in which it generally operates is disclosed in US. Patent2,622,669 issued to V. Z. Caracristi on December 23, 1952. As describedin this patent the fuel and air mixture delivered to the pilot torch isignited by means of a spark plug, and it is very important that theoperator be informed whether or not ignition of the fuel in the torchhas actually taken place and whether or not a pilot flame has beenproduced and is ready to light the ignitable mixture of fuel and airwhich is about to issue from the main burners. Because of the danger ofexplosion it is absolutely necessary that the fuel is only thendischarged into the furnace when and after the pilot torches arepositiveiy lit.

As soon as ignition has taken place of the main burner fuel and the un tis in operation, the flame of the igniter torch is extinguished.However, to guarantee safe operation of the steam generator furnace atall loads, and especially at reduced loads, it is required that eachburner i equipped with a device which will immediately indicateblack-outs or the loss of flame of a main burner. Failure of the burnerto maintain ignition is apt to occur when the burner is made to operateat low capacity, as during reduced load operation. T o forestallpossible explosion of the unburned fuel and air mixture, such blacr-outor ignition failure must immediately be followed by a shutting ofi ofthe fuel and air supply to the burner. Such actions should of course beautomatic and should preferably be free of any possibility of humanfailure.

In addition to the difliculties experienced in translating a burnerblack-out signal into fuel and air shut-off action, it is primarily thedegree of reliability of presentday flame sensing devices which leavesmuch to be desired. Failure of these devices to report loss of flamehave in fact been the cause of at least one recent furnace explosion.

Various means have heretofore been employed to give indication of suchpresence of flame. One device comprises a thermocouple, also calledpilot generator, installed in the wall of the pilot torch or in the wallof the furnace near each burner. The thermocouple in conjunction with arelay system indicates presence of flame by activating a signal at thecontrol board when the temperature in the pilot torch or near the burnerhas risen above the ignition temperature. Another device used for flameindication consists in a so-called fire-eye, making use of a leadsulphide cell being sensitive to the presence of a flame. These devicesrequire very complicated electric and electronic circuitry includingnumerous relays, which equipment when being exposed to the rugged useand environment of a steam power plant, breaks down quite frequently andrequires costly maintenance, replacement and repair. Furthermore, thereliability of the pilot generator and fire-eye device is impaired byaccumulations of ash and slag on the surfaces and parts of the sensingelement thereof, which of necessity are exposed to the intense heatwithin the nozzle or the furnace and which are frequently decomposed bythis heat.

In connection with some types of burners and in furnaces where aplurality of these burners is employed, it has heretofore beennecessary, because of the nature of the sensing devices used, to place asensing device adjacent each burner. In case of loss of fire on oneburner the fuel and air mixture flowing to this burner is shut ofli.This detrimentally effects the air-fuel ratio of the mixture beingdelivered to the remaining burners, thereby greatly increasing thepossibility of the entire furnace to lose ignition and causing acomplete shut down of the steam generator. Such interruption of serviceis undesirable because it increases maintenance cost and decreasesstability of operation and availability of the unit.

My inventive improvement as herein disclosed overcomes or greatlydiminishes the above difficulties through the employment of a superiorindicating system. The functioning of my system is based on reliablepressure differences received by a pressure diflerential switch from thecombustion chamber in question, such as a pilot torch nozzle or anentire furnace, for indicating the presence or absence of combustion orflame Within said combustion chamber. This is accomplished by positiveand dependable means and with practically no delay in action.

It is accordingly a primary object of my invention to provide inconnection with a combustion chamber an improved and reliable flame orcombustion indicating sysitem, one important feature thereof being asensing elernent which is not subject to or exposed to the radiant heatin the combustion chamber.

Another and more specific object of my invention is to increase thedependability, ruggedness and useful life of a flame or combustionindicating system used in connection with the ignition torch and/ or inconnection with the combustion zone of a steam generating furnace.

A further object of my invention is to provide a dependable system andmethod for indicating at a remote point of control, differences incombustion rate or intensity occurring in a combustion chamber atdifferent elevations or zones thereof.

An additional object of my invention is to provide a flame sensingsystem, the sensing element of which is independent of individualburners and has a sensing range which extends over the entire combustionzone or furnace.

Other and further objects of the invention will become apparent to thoseskilled in the art as the description hereof proceeds.

With the aforementioned objects in view, the invention comprises anarrangement, construction and combination of the elements of theinventive organization in such a manner as to attain the results desiredas hereinafter more particularly set forth in the following detaileddescription of illustrative embodiments, said embodiments being shown bythe accompanying drawings wherein:

FIG. 1 is a diagrammatic illustration of a combustion chamber equippedwith the herein disclosed pressure sensing device for flame indication;

FIG. 2 is a diagrammatic illustration of a steam generator having afurnace equipped with my improved flame indicating system, including aschematic diagram illustrating how the various components of my flameindicating system are interconnected for coordinating cooperation;

FIG. 3 is a diagrammatic cross-sectional plan View of a furnace equippedwith tangentially firing corner burners, and showing the associatedigniters or pilot torches in relation therewith;

PEG. 4 is an enlarged plan section through the lower right side cornerof the furnace shown in FIG. 3, through the partially shown burner andside igniter torch associated therewith;

FIG. 5 is an elevational section taken on line 55 of PEG. 4 of a pilottorch and a schematic diagram illustrating how the various components ofmy flame indi cating system are interconnected for coordinatingcooperation;

FIG. 6 is an end view of the igniter nozzle as viewed from line 6-5 ofFIG. 5;

FIGS. 7 and 8 are graphic illustrations of the pressure differencesexisting between two selected points in a combustion chamber, underconditions when the flame is lit or combustion takes place and when theflame is extinguished; with the graph of FIG. 7 more specificallypertaining to the igniter shown in FIG. 5 and the graph of PEG. 8 to thevertical furnace of FIG. 2;

FIG. 9 is a diagrammatic illustration of a furnace chamber bein equippedwith the herein disclosed inventive device for indicating at a remotecontrol station the relative differences in combustion rate or intensityoccurring at various elevations or zones of the furnace chamber.

The Inventive Basic Device Referring now to FIG. 1, an elongatedcombustion chamber it) is bounded by walls 12. Fuel in a gaseous, liquidor pulverized form enters the chamber 14 as by Way of nozzle 14 andafter mixing with air entering by way of slot 1 is ignited as by device17 and burns at least partially within said chamber 1 3. The generatedcombustion gases leave the chamber via outlet 18. A pressuredifferential responsive device 20 is operatively connected to twoopenings 22 and 24 provided in the wall 12 of chamber lb, suchconnection being effected by conduits 25 and 23 respectively. Device 2taccordingly maintains static pressure communication with the interior ofchamber iii. The opening 22 is located adjacent the fuel and air inletend and the opening 24 adjacent the combustion gas outlet end of chamber10.

If combustion is absent in chamber Zltl and the effect of air flow isneglected, the static pressure P, measured at 22 is found to be the sameas the static pressure Q measured at 24-. The pressure differentialresponsive device 263 accordingly records a diflerential pressure ofzero. However, as soon as the fuel and air mixture is ignited andcombustion is taking place within chamber lit the static pressure Pobserved at the fuel inlet end rises and the static pressure Q observedat the gas outlet end drops, so that a positive pressure differentialP-Q is almost instantly indicated by instrument 20. It is thisphenomenon of change in pressure differential between a state ofcombustion and a state of noncombustion which is being made use of in myherein disclosed novel flame and combustion indicating system.

The Environment Although my inventive control system can be employed inconnect on with many diflerent combustion chambers or furnaces andburning all types of fuel, only two important applications thereof willnow be described. Such description is intended to be illustrative onlyof two out of many possible applications, and is not to be interpretedas being restricted to the use thereof in the steam boiler furnace or inthe pilot torch organization herein described.

Referring now to the FIGS. 2 and 3, there are shown in diagrammatic forman elevational section and a plan cross section through a combustionchamber 10, here specifically designated as furnace chamber 3% of asteam generator. Four main burners 32 are arranged in the four cornersof the chamber 3% for discharging streams of fuel and air for burning indirections tangential to an imaginary firing circle 34. A so-called sideigniter or pilot torch 36 (see FIG. 3) is positioned adjacent eachburner 32 for igniting the fuel issuing therefrom at the proper time.These side igniters or pilot torches 36 are associated with burners 32in the manner illustratively shown in FIG. 4 in an enlar ed scale. Thewalls of furnace 30, as shown in FIG. 2, are generally lined with watercarrying and steam generating tubes 38.

The combustion gases rising in the furnace 30 enter a horizontal gasoutlet passage containing superheater 42, which may be followed by avertical down-draft gas passage (not shown) in which additional heatabsorb ing surfaces may be disposed such as an economizer and an airheater (not shown).

The Flame Sensing Apparatus as Applied to Igniter Torch 36 An importantapplication of my flame sensing apparatus and method is illustrated inFIGS. 4 and 5.

The illustrative igniter torch 36 shown is adapted to burn oil. However,the novel control and indication facilities of the present inventionalso can be used with igniter torches which are fired by fuels otherthan oil such as gas, for example. The igniter torch 36 is mountedadjacent main burner nozzle 32 and comprises a mounting plate 46, torchhead 48, torch nozzle 5%), spark plug 51, an atomizer 52, the interiorof nozzle 5%? representing combustion chamber lit. The mounting plate 46supporting the igniter torch 35 is bolted onto the furnace casing 54,the mounting plate 46 being shielded against heat by insulation 47.Nozzle 54) is suspended from the mounting plate 46 by means of bracket55. One end 56 of the nozzle is round, and, as here shown, the other endis flared in one direction and contracted at right angles thereto toform along narrow opening 57 through which a sheet of flame 58 issues.may be used to ignite another fuel stream 59, FIG. 4, issuing from anadjacent main burner 32, which maybe tilted to direct the fuel stream 59upwardly or downwardly or to any intermediate position. shape of thepilot torch nozzle 5'0 assures adequate flame distribution at all tiltpositions of the adjacent main burner 32.

The pilot torch head 48 comprises a body portion forming an internalchamber 6%), open toward the nozzle 50 and having openings for receivingspark plug 51 and atomizer 52. The pilot torch head 48 is also providedwith peripherally disposed air inlet vanes 62 to impart to V ply tube65. The resultant air and oil mixture is dis charged into chamber 60 andignited by the spark formed between electrode 66 of the spark plug 51and the beveled face 67 of the torch head 48. The rotating secondarySuch a flaring nozzle The flaring air entering through vanes 62 promotesa desirable mixing action and minimizes harmful fly ash settlement,while the burning mixture is flowing through nozzle 50 and issuing fromopening 57 in a hot luminous flame.

Flame Indicating Functions T 0 Be Achieved in Connection With IgniterTorch In commercial installations of boiler furnaces of the highcapacity type diagrammed in FIG. 2 it is desirable to organize the mainfurnace burners such as 32 for complete control and supervision in partby an operator located at a centralized control point remote from thefurnace, and in remaining part by automatic apparatus similarly located.In furtherance of this objective each of the main burners 32 is equippedwith its individual igniter torch 36.

The problem then is, while an operator is enabled at a centralizedcontrol point remote from the furnace to bring torches 36 into action atthe furnace when it is desired to light up their associated main burners32, to receive back from each torch a reliable indication that ignitionof the fuel in the torch has been actually obtained. For reasons ofsafety it is absolutely essential that such indication be receivedbefore a fuel and air mixture is discharged into the furnace through themain burners 32.

Utilized to accomplish this particular function is a pressuredifferential responsive device 2%) in the form of switch 68, FIG. 5,installed in a control box 69. This switch comprises two pressurechambers 76 and 71 separated by a diaphragm 72, and a rod 73 one endthereof being fixedly attached to diaphragm 72 and the other endorganized to open or close electric contact switch 74 and contact switch75 by means of bar 76. An adjuster 77, including spring 78 serves tokeep contacts 74 closed when the pressure in chamber 71 fails to exceedby a predetermined amount the pressure existing in chamber 76. Chamber70 is connected by way of conduit 79 to a pressure tap 89 secured inopening 24 located in the wall of nozzle 59 adjacent the outlet endthereof, and chamber 71 is connected by way of conduit 81 to a pressuretap 82 secured in opening 22 located in the torch head 48 near the fuelinlet end of the pilot torch. Therefore the pressure prevailing inchamber 76) corresponds to the static pressure existing in the vicinityof the opening 2 at the gas outlet of the torch, and the pressureprevailing in chamber 71 corresponds to the static pressure existingnear the opening 22 or at the fuel inlet of the torch.

When the pilot torch 3-5 is out of operation, the static pressure at thefuel inlet (chamber as and at the flame outlet end 57 are practically ofthe same magnitude, if friction losses are neglected. However, when thetorch is lighted and a flame is burning, a substantially higher pressureexists at the fuel in et end opening 22 or cham ber 71 than at the flamedischarge end, or chamber 7%. When this pressure difference attains apredetermined value to overcome the tension of spring 78 the contacts 74will open and the contacts 75 will close. Closing of contacts 75energizes an electric circuit 34 and actuates a signal device such as agreen light bulb 85. Closing of contacts 74 energizes electric circuit86 and actuates a signal device such as red light bulb 87. Signaldevices 85 and 87 are located at a central control point and serve toindicate to the operator whether or not a flame is issuing into thefurnace from pilot torch 36, in a manner which will now be described.

Assuming, for example, that the excess of static pressure measured atopening 22 over that measured at opening 24, when the pilot torch islighted is established by tests to be 2 inch VLG. Then the adjuster 77may be set, so that an excess of pressure of 1 /2 inch W.G. in chamber71 over that existing in chamber 743 will open switch contacts 74 andclose switch contacts 75.

This is graphically illustrated in FIG. 7, where are shown three sets ofpressure conditions. The first set indicates the pressures, a and b,respectively, prevailing at openings 22 and 24 when the flame is lit;and the second set indicates the pressures c and d, respectively, whenthe flame is extinguished. A friction loss of 0.25 is assumed to existdue to air flow through the nozzle 59. The third set of pressurereadings A and B indicates the controlling pressure differential (1.5inch W.G.) at which the pressure switch 68 is set to act. Thus as thepressure difference drops from the 2 inch W.G. value (flame lit) to the0.25 inch W.G. value (flame out) it passes through the 1.5 inch WG.value at which switch 68 is set for atcion.

This means that when the torch is out of operation and without a flamethe contacts of switch 743 will be closed and a red bulb $7 will lightup warning the operator that the torch 36 is not in readiness to igniteany fuel that may be discharged into the furnace by way of main burner32. However, as soon as ignition has been established in the pilot torchnozzle the contacts of switch 74 will open extinguishing red light 87and switch 75 will close lighting up green bulb 85. This will be anindication to the operator that a flame is issuing from nozzle 59 andthat it is safe to discharge fuel through the main burners 32 into thefurnace. If, for some reason, the flame in nozzle 5% should beextinguished, then the pressure differential between pressure taps Sitand 82 will drop below 2 inch W.G. causing contacts 75 to open andswitch 74 to close, and green light 85 to go out and red light 87 tolight up.

Flame Indicating Functions T 0 Be Achieved in Connection With Furnace 30During normal operation of the furnace 3f the pilot igniters 36associated with main burners 32 are generally extinguished. Undercertain conditions of low load operation or when low grade fuel isburned the possibility exists of losing total ignition in the furnace.As earlier pointed out herein such loss of flame is dangerous because ofthe explosive nature of the unburned comminuted fuel mixed with heatedair that is entering the furnace. In such an event the feeding of thefuel must be immediately stopped and the furnace must be scavenged ofunburned fuel before the burners can again be lighted.

My flame indicating method and system as herein disclosed, because ofits simplicity and reliability, is exceptionally well adapted tofunction both in warning the operator, such as by an alarm bell or thelike, that the fire has gone out, and/ or in automatically shutting offthe fuel fed to the main burners in case ignition is lost in thefurnace. How this is accomplished will now be described.

The burners 32 of the steam boiler as diagrammatically illustrated inPEG. 2, are supplied with comminuted fuel from a source not shown viafuel pipes 88 and 99. An automatically operated fuel valve 92 isinstalled in pipe 9% and serves to shut off the flow of fuel to theburners 32 when desired. Although one single valve is here shown tocontrol the fuel flow to all burners of a tangentially fired furnace 3%,such showing is considered merely representative, and my inventive flameindication system an fuel flow control can with equal benefit be appliedto furnaces employing other types of burners and firing. Such furnacesmay discharge fuel from a row of burners disposed in one or two walls orin the roof thereof. In these cases it may be advantageous to provideeach individual burner with a flame indication system and fuel flowcontrol in the same manner as herein described and illustrated in FIG.2.

Two pressure connections 93 and @4 are provided in the wall of thefurnace 3%, one 93 in connection with opening 22 below or at the burnerelevation, and the other 94 in connection with opening 24 in the upperpart of the furnace. The relative location of these pressure connectionsis not critical except that the lower connection 93 should preferably belocated in the fuel discharge zone and the upper pressure connection 94in a zone where combustion of the fuel has been well established or ispartially completed. These connections 93 and 94 serve the purpose ofobtaining relative indications of the static pressure prevailing in thefurnace in the vicinity of respective openings 22 and 24. The valuesobtained may be positive or negative. A furnace operating under suctionwill give negative values. However, whether positive or negative valuesare obtained is relatively unimportant, since it is the pressuredifferential between pressure points 93 and 594 or openings 22 and 24which is being utilized in my herein disclosed system of flameindication.

In an upright furnace chamber, such as that diagramrncd in FIG. 2 wherethe combustion gases flow in a vertical direction, the chimney er ect ofthese hot gases must be taken into consideration in the evaluation ofthe pressure difierential between connection 93 and 94. This holds trueregardless of whether the fuel is ignited in the lower portion of thefurnace, the gases flowing upwardly and leaving by way of a top gasoutlet, or is ignited in the upper portion of the furnace, the gasesflowing downwardly and leaving by way of a bottom gas outlet.

Thus in a furnace of the type shown in FIG. 2 when in operation, i.e.,when fuel is burned therein, the static pressure at point 94 maygenerally be maintained at a negative value of 0.5 inch W .G., whereasthe furnace zone at point 93 would be under greater suction due to thestack effect of the heated gases. The pressure at 93 accordingly may be,for instance, l.O inch W.G., this value depending on the height of thefurnace chamber, the temperature and velocity of the gases.

When total loss of ignition occurs in the furnace and the flame isextinguished the static pressure at 93 rises, for example to ).25 inchW.G., with the static pressure at point 94 kept at a normal value of 0.5inch VG. by automatic control of the induced draft fan. Thus it is seenthat a drop in pressure differential between point 93 (which correspondsto P of FIG. 1) and point 94 (which corresponds to Q of FIG. 1), inindicative of loss of ignition in the furnace chamber 39.

These conditions are graphically illustrated in FIG. 8 where, as in FIG.7, are shown three sets of pressure conditions. The first set indicatesthe pressures e and 1, respectively, prevailing at pressure connections93 (opening 22) and 94 (opening 24) when the flame is lit; and thesecond set g and h, respectively, when the flame is out. The pressuredifferential between e and f of 0.5 inch W.G. is arbitrarily here givena negative value because it falls below the pressure line of 0.5 inchW.G. which is the negative pressure generally maintained at the topoutlet of the furnace. in distinction thereto the pressure differentialbetween points g and h of +0.25 inch W .G. is given a positive valuebecause it falls above said i).5 inch W.G. pressure line.

The change in pressure differential upon loss of fire, when transmittedto a pressure differential switch 95 functioning as the pressuredifferential responsive device 2%, actuates magnetically operated fuelvalve 92 to shut off the flow of fuel to burners 32, and at the sametime trips an alarm device 97 to inform the operator of the loss of tirein the furnace.

To accomplish these functions chamber 1% of pressure switch 95 isconnected to pressure point ddby way of conduit 99, and chamber 98 isconnected to pressure point 93 by way of conduit M1. The diaphragm 1G2separating chambers 93 and 142% carries an extension rod P33, the freeend of which is organized to open or close electric contact switches 1ndand Th5 by means of connecting bar 1%. The closing of switch 1 3-4energizes a circuit generally designated 1&7, thereby actuating anindication device as by lighting a green bulb M3. The closing of switchM55 energizes a circuit generally designated 109, thereby setting olf analarm device 97, and at the same time energizes a circuit 11.1 causingfuel valve 92 to close by action of the solenoid ll Valve 92 is shown asnormally being held in the open position by a spring 112. Energizationof circuit 116 causes plunger '8 of solenoid 111 to enter the windingthereof thus overcoming the pull of spring 1512 and closing valve 92.

Pressure diifcrential switch is normally biased by spring 113, thetension thereof being controlled by adjuster 114, to keep contacts 105closed and contacts 104 open. As soon as the excess pressure in chamberover that prevailing in chamber 93 exceeds the tension of spring 113contacts Hi5 will open and contacts 104 will close thereby energizingcircuit 107 and lighting green bulb Hi8, which will stay lit as lont asthe pressure in chamber 98 does not rise above a predetermined value.This indicates to the operator that combustion in the furnace isproceeding without interruption.

In practice the most suitable pressure differential that determines thetension of spring 113 or the setting of adjuster 114 is obtained bytests conducted at the time when the unit is first put into operation.Thus the largest pressure diflerential between point Q3 and 94, i.e.,the lowest static pressure at point 3 with respect to point 94, would beobserved when the unit is operating at maximum capacity and the higheststatic pressure when the unit is operating at its lowest capacity. Sincea still higher presure at point 93 is obtained when the fire is totallyextinguished, a pressure differential value may be chosen for thesetting of adjuster 114 which lies between the pressure differentialobtained when the flame is out but the furnace is still hot, and thevalue obtained when the furnace is operating at the lowest permissiblecapacity.

Thus returning to the earlier mentioned practical example as illustratedin PEG. 8, it was assumed that the pressure differential between points94 and 93 or between chambers 1% and 98 has a value of 0.5 inch W.G.when the burners 32 are burning a suflicient amount of fuel to operatethe unit at its lowest capacity, and the said pressure differentialdrops to +0.25 inch W.G. when loss of total ignition occurs in thefurnace. Under these assumed conditions therefore the adjuster 117controlling the tension of spring 113 must be so set that the electriccontact switch res will open and contact switch will close during thetime when the higher pressure differential between points 93 and 94,drops from a value of 0.5 inch W.G. to a value of +0.25 inch W.G. or atotal of 0.75 inch W.G. For instance, spring 113 would be set undercertain operating conditions to trip at a pressure differential of 0.1inch W.G. This is shown by the third set of pressure readings C and D inFIG. 8 indicati ing the controlling pressure difierential of 0.1 inchW.G. at which the pressure switch 95 is set to act. Thus as soon as lossof ignition in the furnace occurs and the pressure differential dropsfrom 0.5 inch W.G. (flame lit) to +0.25 inch W.G. (flame out), switch 1%will:

Visual Indication of Relative Combustion Rates To Be Achieved Referringnow to FIG. 9, showing the furnace 311} in greatly simplified form, fueland air for combustion is fed to furnace 3b via burners 32, the gasesleaving by way of furnace outlet 40. According to the invention furnacechamber 34? is equipped with a combustion sensmg system including anindicator or multiple pressure gauge 116 for registering the relativestatic pressures prevailing at various elevations or zones in furnacechamber 3%. For this purpose there are provided in the wall of thefurnace at successive elevations a series of openings. 117 through 123for receiving pressure taps, each tap in turn being operativelyconnected to one of a corresponding series of pressure gauges 124 to 13%inclusive, conveniently assembled in indicator 116 for easy comparison.

in accordance with the herein disclosed invention the relative staticpressure differential between two pressure 9. taps, spacedly located indirection of gas flow in the furnace Wall, affords a measure of therelative combustion rate or combustion intensity existing in the zone between the said two points. This is diagrammatically illustrated by gauge116, affording a visual indication of the varying combustion intensitiesthroughout the height of the furnace by registering the static pressuresprevailing at successive elevations in the furnace, with the lowermostpressure tap 123 showing the highest suction in gauge 1'39, and thehighest pressure tap 117 showing the lowest suction in gauge 124.

Thus, for example, the location or elevation of the flame in the furnacechamber can be determined with comparative ease and certainty at acontrol station remote from the furnace. Also the relative rate ofcombustion at different locations in the furnace can be ascertained fromthe relative distance between static pressure readings. For instance, asillustratively shown in FIG. 9, the combustion rate in the zone betweenpressure taps 117 and 118 would be considerably smaller and less intensethan that existing in the zone between pressure taps 122 and 123 asindicated by the smaller pressure differential between suction readingsof gauges 124 and 125 when compared with the larger differential shownbetween readings of gauges 12? and 134 These and similar readings, ofcourse, are obtained only While a fire is burning in .the furnacechamber 30. If ignition should be lost and combustion cease, the picturepresented by indicator 116 will immediately and radically change. Insuch an emergency the suction readings of gauges 125 through 130 willdrop to the value of, or go even beyond the value of, the reading shownby gauge 124 which records the static pressure generally maintained inthe top of the furnace. This drop is indicated by dotted line 132.

' While I have shown in FIG. 9 the pressure conditions that aregenerally encountered in a vertical furnace operating undersubatmosphen'c pressure, it must be understood that these conditions.may change when my invention is applied to a horizontal furnace or to afurnace fired from the top, or to a furnace operating under a staticpressure higher than atmospheric. Although the operating conditions ofthese various furnace types may be different the basic concept uponwhich my invention is founded remains the same. This concept may bedefined as a recognition and realization of the fact that the absence orpresence as well as the degree or intensity of combustion taking placein any given combustion zone of a furnace chamber is immediately andwith fair accuracy reflected in the static pressure differentialobserved between a point upstream and a point downstream of said zone,in the gasflow sense. This concept has been made use of in devising theherein disclosed system and method of flame or combustion indicationobservable and acting at a control point remote from the furnacechamber, and offering the important advantage of possessing a sensingelement which is not subject to the heat of the furnace nor toaccumulations of slag or ashes, as are other similar devices. My flameand combustion indicating system and method is therefore far superior toother systems as used heretofore, because of the simplicity inconstruction, ruggedness in service and dependability in operation whichit affords.

While illustrative embodiments of this invention have been shown anddescribed, it will be understood that changes in construction,combination and arrangement of parts may be made Without departing fromthe spirit and scope of the invention as claimed.

What I claim is:

1. In a steam generating furnace having means for detecting the loss offlame in a burner apparatus appended thereto and being provided with achamber comprising a fuel receiving and ignition zone and a fuel burningzone downstream therefrom, and having means to provide a gaseous mixtureof fuel and air to said fuel receiving and ignition zone, said chamberlocated to discharge into said furnace; the combination of the meanssubject to a first static pressure existing inside said chamber withinsaid fuel receiving and ignition zone for indicating said first pressureexteriorly of said chamber; means subject to a second static pressureprevailing in said fuel burning zone and for indicating said secondstatic pressure exteriorly of said chamber; means for determiningvariations in the differential between said first static pressure andsaid second static pressure; a control device for responding tooperating conditions of said burner apparatus; means for operating saiddevice; and means governed by said pressure differential variations forcausing said control device to respond when said pressure differentialdrops to a predetermined value, whereby loss of flame within saidchamber is readily detected, such detection being independent of andunaffected by ambient static pressure conditions existing exteriorly ofthe fuel and air inlet end as well as exteriorly of the flame dischargeend of said chamber.

2. In a steam generating furnace having means for detecting the loss offlame in a burner apparatus appended thereto and being provided with achamber having a fuel and air inlet and a fuel burning zone downstreamtherefrom, and having means to provide a gaseous mixture of fuel and airby Way of said fuel and air inlet, said chamber located to dischargeinto said furnace; the combination of means subject to a first staticpressure existing inside said chamber adjacent the fuel and air inletthereof and for indicating said first pressure exteriorly of saidchamber; means subject to a second static pressure existing in theinterior of said chamber adjacent the flame discharge end thereof andfor indicating said second static pressure exteriorly of said chamber;means for determining variations in the differential between said firststatic pressure and said second static pressure; an alarm deviceincluding means for activating said alarm device; and means governed bysaid pressure differential variations for causing said alarm to respondwhen said pressure differential drops to a predetermined value, wherebyloss of flame within said chamber is readily detected, such detectionbeing independent of and unafiected by ambient static pressureconditions existing exterioriy of the fuel and air inlet end as well asexteriorly of the flame discharge end of said chamber.

3. In a steam generating furnace having means for detecting the loss offlame in an igniter apparatus appended thereto and being provided with achamber having a fuel and air inlet and a fuel burning zone downstreamtherefrom, and having means to provide a gaseous mixture of fuel and airby way of said fuel and air inlet, said chamber located to dischargeinto said furnace; the combination of means subject to a first staticpressure existing inside said chamber adjacent the fuel and air inletthereof and for indicating said first pressure exteriorly of saidchamber; means subject to a second static pressure existing in theinterior of said chamber adjacent the flame discharge end thereof andfor indicating said second static pressure exteriorly of said chamber; apressure switch subject to variations of the differential between saidfirst static pressure and said second static pressure for indicatingVariations of said differential at a point remote from said chamber; asignal device including means for activating said signal device; andmeans governed by the action of said pressure switch for causing saidsignal device to be activated when said pressure differential hasattained a predetermined high value found to be indicative of combustionwithin said chamber, the accuracy of said activation being independentof and unaffected by ambient static pressure conditions existingexteriorly of the fuel and air inlet end as well as exteriorly of theflame discharge end of said chamber.

4. In a vapor generating furnace having means for detecting the loss offlame in a burner apparatus appended thereto and being provided with acombustion chamber comprising a fuel receiving and ignition zone and afuel burning zone downstream therefrom, and having means to provide agaseous mixture of fuel and air to said fuel receiving and ignitionzone, said chamber located to discharge into said furnace; thecombination of means to sense a differential of static pressure existingin the interior of said chamber between a point adjacent said fuelreceiving and ignition zone and a point located remotely therefrom inthe direction of combustion gas travel and Within the burning zone ofsaid combustion chamber, and to indicate said pressure differential at apoint outside of said combustion chamber; an alarm device includingmeans for transmitting impulses from said pressure differential sensingmeans to said alarm device; and means governed by said pressuredifferential for ctivating said alarm device when said pressuredifferential attains a value of a magnitude indicative of combustiontaking place within said combustion chamber, whereby presence of flameWithin said chamber is readily detected, such detection beingindependent of and unaffected by ambient static pressure conditionsexisting exteriorly of the fuel and air inlet end as well as exteriorlyof the flame discharge end of said chamber.

5. In the operation of a steam boiler having a furnace chamber firedwith a mixture of air and finely divided fuel suspended in air, saidmixture being discharged into said chamber by way of a burner andforming an explosive mixture prior to ignition thereof, said chamberbeing subject to an interior static pressure variable with respect toatmospheric pressure and having an igniter torch including an ignitertorch housing for discharging a flame into said furnace chamber fromsaid housing to ignite said mixture, the method of detecting thepresence of said igniter flame issuing from said housing, comprisingthesteps of obtaining a first static pressure reading at a first pointwithin said housing, obtaining a second static pressure reading in thecombustion zone Within said housing at a second point spaced downstreamfrom said first point in the flame travel sense, dhferentiating saidfirst pressure reading against said second pressure reading to obtain apressure differential, determining the said pressure differential in theabsence of flame and in the presence of flame, and utilizing thesedetermined pressure differentials in a control device responding to aflameon condition or a flame-off condition which is independent of andunaffected by the atmospheric static pressure prevailing outside of saidchamber and the static pressure prevailing inside of said chamber.

6. In a furnace for burning fuel suspended in air and provided withmeans to receive both fuel and air in a fuel receiving zone and to burnsaid fuel in a fuel burning zone, said furnace having water cooled wallsfor the generation of steam and having a furnace outlet remote from saidfuel receiving zone to discharge the gaseous products of combustion; thecombination of a series of successive openings provided in the watercooled wall of said furnace at locations in the fuel burning zone andspaced from each other generally in the gas flow sense; means forobtaining through said openings impulses of the static pressureprevailing in said furnace at said locations, said fuel burning zonebeing an unobstructed flow passageway, with the pressure differentialbetween any two of said openings constituting a direct indication of therate of combustion prevailing in the furnace zone portion between thesaid two openings, and said indication being unaffected by any otherfactors; and means to convert said impulses into an intelligent displayindicating the relative combustion rates prevailing in the furnace zoneportions between said openings.

7. In a furnace for burning fuel suspended in air and adapted to receiveboth fuel and air in a fuel receiving zone and to burn said fuel in afuel burning zone, said furnace having water cooled walls for thegeneration of steam and having a furnace outlet remote from said fuelreceiving zone for discharging the gaseous products of combustion; thecombination of a series of successive openings provided in the watercooled wall of said furfrom each other generally in the gas flow sense;pressure taps inserted into said openings for obtaining readings of thestatic pressure prevailing in each furnace zone surrounding one of saidopenings, said fuel burning zone being an unobstructed flow passageway,with the pressure differential between any two of said readingsconstituting a direct indication of the combustion intensity prevailingin the furnace portion between the two openings from which the said tworeadings are taken, and said indication being unaffected by any otherfactors; a multi-reading pressure gauge adapted for recording saidvarious static pressure readings side by side in the same succes siveorder in which the corresponding pressure taps. are located in thefurnace wall; and means for transmitting said static pressure readingsto said multi-reading pressure gauge; whereby a composite picture isobtained of the relative combustion intensities prevailing in thefurnace zones between said openings. 7 i

8. In a fuel burning and steam generating apparatus having a furnacechamber adapted to receive fuel suspended in air in a fuel receivingzone and to burn said fuel in a fuel burning zone prior to discharge ofthe products of combustion through a furnace outlet, said furnacechamber having water cooled walls for the generation of steam, themethod of indicating the rate of combustion in a series of furnace zonessuccessively disposed in the gas flow sense in the burning zone betweenand including said fuel receiving zone and said furnace chamber outlet,each zone having an opening in the wall of the furnace chamber forreceiving a pressure tap; comprising the steps of obtaining anindividual static pressure indication from each of said furnace zonesvia the respective pressure taps, said furnace zones forming anunobstructed flow passage- Way, with the pressure differential betweenany two of said furnace zones constituting a direct indication of therate of combustion prevailing in the furnace zone between the said tworespective pressure taps, and said indication being unaffected by anyother factors; translating said static pressure indications into visualimpression receiving means at a control station separated from saidfurnace chamber; and relating said impressions with each other in thesuccessive order of said furnace zones to obtain a composite of therelative combustion rates prevailing in' said series of successivelydisposed furnace zones. 7

9. In a furnace for burning fuel suspended in air an provided with meansto receive both fuel and air in a fuel receiving zone and to burn saidfuel in a fuel burning zone, said furnace having an uprightly elongatedshape and being provided with a furnace outlet remote from said fuelreceiving zone to discharge the gaseous products of combustion; thecombination of a plurality of successive openings provided in the wallof said furnace at locations spaced from each other generally in the gasflow sense;

means for obtaining through said openings impulses of the staticpressure prevailing in said furnace at said locations,

with the pressure differential between any two of saidv openingsconstituting a direct indication of the rate of combustion prevailing inthe furnace zone between any two of the said openings, and saidindication being unaffected by any other factors; and means forresponding to said impulses to indicate the combustion rates prevailingin the furnace zone portions surrounding said openings.

10. In the operation of a steam boiler having a furnace chamber firedwith a mixture of air and finely divided fuel suspended in air, saidmixture being ischarged into said chamber by way of a burner and formingan explosive mixture prior to ignition thereof, said chamber beingsubject to an interior static pressure variable with respect toatmospheric pressure and having means for igniting said' mixture andproducing a flame, the method of detecting the presence of said flamewithin said chamber, comprising the steps of obtaining a first staticpressure reading within said chamber and ahead of the normal point ororigin of said flame in the flame travel sense, obtaining a secondstatic pressure reading in the combustion zone Within said chamber andbeyond the normal point of origin of said flame in the flame travelsense, differentiating said first pressure reading against said secondpressure reading to obtain a pressure differential, obtaining the saidpressure differential in the absence of flame and in the presence offlame, and utilizing these obtained pressure differentials in an impulsereceiving means, whereby a flame-on condition or a flame-01f conditionis determined in a manner which is totally independent of and unaffectedby the atmospheric References Cited in the file of this patent UNITEDSTATES PATENTS 1,630,977 Smoot May 31, 1927 14 Roucka Nov. 22, JohnsonMar. 23, Turner Aug. 8, Hourvitz Apr. 17, Caracristi et a1. Dec. 23,Cumming Dec. 7, Perchonok Apr. 3, St. Clair June 17, Lewis et a1 Nov.10,

FOREIGN PATENTS France Mar. 18, Germany Jan. 13,

1. IN A STEAM GENERATING FURNACE HAVING MEANS FOR DETECTING THE LOSS OFFLAME IN A BURNER APPARATUS APPENDED THERETO AND BEING PROVIDED WITH ACHAMBER COMPRISING A FUEL RECEIVING AND IGNITION ZONE AND A FUEL BURNINGZONE DOWNSTREAM THEREFROM, AND HAVING MEANS TO PROVIDE A GASEOUS MIXTUREOF FUEL AND AIR TO SAID FUEL RECEIVING AND IGNITION ZONE, SAID CHAMBERLOCATED TO DISCHARGE INTO SAID FURNACE; THE COMBINATION OF THE MEANSSUBJECT TO A FIRST STATIC PRESSURE EXISTING INSIDE SAID CHAMBER WITHINSAID FUEL RECEIVING AND IGNITION ZONE FOR INDICATING SAID FIRST PRESSUREEXTERIORLY OF SAID CHAMBER; MEANS SUBJECT TO A SECOND STATIC PRESSUREPREVAILING IN SAID FUEL BURNING ZONE AND FOR INDICATING SAID SECONDSTATIC PRESSURE EXTERIORLY OF SAID CHAMBER; MEANS FOR DETERMININGVARIATIONS IN THE DIFFERENTIAL BETWEEN SAID FIRST STATIC PRESSURE ANDSAID SECOND STATIC PRESSURE; A CONTROL DEVICE FOR RESPONDING TOOPERATING CONDITIONS OF SAID BURNER APPARATUS; MEANS FOR OPERATING SAIDDEVICE; AND MEANS GOVERNED BY SAID PRESSURE DIFFERENTIAL VARIATIONS FORCAUSING SAID CONTROL DEVICE TO RESPOND WHEN SAID PRESSURE DIFFERENTIALDROPS TO A PREDETERMINED